1. Field of the Invention
The present invention relates generally to telecommunications networks. More particularly, the present invention relates to managing a telecommunications network containing diverse network elements conforming to a variety of telecommunications protocols.
2. Related Art
As telecommunications networks become more complex, telecommunication network service providers require increasingly capable network management systems. The network management systems face substantial hurdles to acceptance by network service providers. One such hurdle is that the network management systems have to manage networks comprised of network equipments that comply with a variety of interface standards. An example of such an interface standard is the well-known common management interface protocol (CMIP). Not only must a telecommunications network management system manage diverse network elements, but it must also manage network growth and/or modification. Conventional telecommunication network management systems do not provide a mechanism for representing the physical network in an efficient manner to facilitate network design and maintenance. Nor do they adequately provide for representing a physical network's evolution to a new configuration.
Moreover as the networks become more capable telecommunication services providers are faced with increased service demand. Increased service demand, in turn, requires increased communication bandwidth. To meet the increased communication bandwidth requirements, many service providers have turned to optical communications. In response to the increased demand for optical telecommunications equipment, a number of vendors have entered the marketplace. To allow telecommunications network designers to connect equipments from various vendors together into a heterogenous fiber optic telecommunications networks, synchronization (also referred to as timing) interconnectivity standards had to be developed. One such standard is the Synchronous Optical NETwork (SONET). An overview of SONET can be found in John Bellamy, Digital Telephony, 403-26 (John Wiley & Sons, Inc. 1991), hereby incorporated by reference.
A SONET network distributes synchronization in the SONET optical signal rate. To do so, a source clock produces an electrical timing signal to be distributed. The source clock is an extremely stable clock. Such a clock is generally referred to as a Stratum-1 source. A Stratum-1 source is a highly reliable timing source (having a free running inaccuracy on the order of one part in 10.sup.11).
The electrical timing signal feeds a frequency multiplier in a SONET transmitter. The frequency multiplier multiplies the timing signal to generate a derived SONET optical signal rate. The SONET transmitter transmits data to a SONET receiver at the derived optical signal rate. The SONET receiver extracts the derived optical rate. The SONET receiver divides the extracted optical rate by the multiplication factor applied by the frequency multiplier to produce the distributed electrical timing signals.
SONET equipment can adapt to network equipment failure by modifying the synchronization topology of the network. However, such modification may cause problems in the resulting network synchronization topology. For example, the modification can result in timing loops and loss of traceability to a Stratum-1 source. Modern networks ensure traceability of timing back to a Stratum-1 source to ensure timing stability. A timing loop occurs when a particular piece of timing equipment is referred to more than once in a particular path. A path connects a source of timing to a user of timing. A timing loop can result in the complete loss of a particular path. This is because the path's timing continually tries to catch itself, eventually culminating in the loss of synchronization. Thus, it is desirable to design a telecommunications network that does not have timing loops, and that has traceability back to Stratum-1. Moreover, as a telecommunications network reconfigures itself to circumvent network failures, the restored configuration must avoid timing loops and maintain Stratum-1 traceability.
What is required therefore is a telecommunications network management system to aid in the design and maintenance of a robust telecommunications network. The system should be capable of managing diverse network equipments conforming to a variety of interface standards. The system should also be able to determine the current state of a network, restore it to a state satisfying various engineering design guidelines. The network management system should be flexible enough to allow upgrades (i.e., addition of new equipment and changes in network topology) without violating the engineering design guidelines.